Can't pass callback to worker functions

The docs are saying that we can pass functions between worker and main thread, but looks like this is only true on one side. I can pass a callback from Worker to Main Thread but I can not pass it from Main Thread to Worker.

Here is the code I used to test (disregard the timeout. I used it only to prevent race conditions)

const testScript = `
  window.analytics = [];
  window.analytics.track = (title, cb) => {
    console.log('Logging analytics.track arguments', {title, cb});
    cb();
  };
  window.addEventListener('click', () => {
    console.log('Worker > Main Thread callback')
  });
`;

<script
  dangerouslySetInnerHTML={{
    __html: `
      setTimeout(() => {
        window.analytics.track('My event', () => {
          console.log('Main Thread > Worker callback')
        });
      }, 3000);
      partytown = {
        forward: ['analytics.track'],
      };
    `,
  }}
/>
<script type="text/partytown" dangerouslySetInnerHTML={{__html: testScript}}/>

And this are the logs I see in the browser after reloading the page and clicking

As we can see the Main Thread > Worker callback never shows and we can see that the callback is an empty function inside the worker.

[steve8708]

Very cool. If you’re game to take a stab at it and send a PR that passes build and adds an additional test for this, that would be great

[cameronbraid]

I need something like this.